Fix small bug in IA2TextInfo.getTextRange when retrieving an empty ra…

…nge (#9029)

* Fix small bug in IA2TextInfo.getTextRange when retrieving an empty range

* Return early when expanding to a mouse unit and there is no text

source/NVDAObjects/IAccessible/__init__.py

@@ -148,6 +148,8 @@ def expand(self,unit):
 		super(IA2TextTextInfo,self).expand(unit)
 		if isMouseChunkUnit:
 			text=self._getTextRange(self._startOffset,self._endOffset)
+			if not text:
+				return
 			try:
 				self._startOffset=text.rindex(u'\ufffc',0,oldStart-self._startOffset)
 			except ValueError:
@@ -199,7 +201,7 @@ def _getLineCount(self):
 
 	def _getTextRange(self,start,end):
 		try:
-			return self.obj.IAccessibleTextObject.text(start,end)
+			return self.obj.IAccessibleTextObject.text(start,end) or u""
 		except COMError:
 			return u""